A recording of this presentation is available HERE.
Thanks to Dr. George Kavalam for an important presentation on AKI.
Here are my take homes:
- Baseline creatinine (SCr) is the lowest value in the last 3 months
- KIDOGO criteria defines AKI as a rise in SCr of 0.3 (in 48 hours) or oliguria (urine output <30cc/hour)
- SCr can be falsely low in muscle wasting, liver disease, and volume overload>> use cystatin C in these circumstances to more accurately detect GFR
- SCr and GFR have an inverse non linear relationship, so a rise from 1-2 is MUCH more concerning than a rise from 3-4
Urinalysis with micro is a "poor man's biopsy"
Urine specific grafity 1.002 is VERY dilue. . . . 1.030 is highly concentrated
Protein: only looks at albumin (cannot assess other proteins, e.g. Benz Jones)
Blood: +blood on dipstick with 0 RBC is rhabdo until proven otherwise
WBC: elevated in infection AND acute interstitial nephritis (AIN)
Ketones: do not detect beta hydroxybutarate
Glucose: a blood glucose >180 will spill into the urine
Urine sediment:
RBC cast>> glomerulonephritis
WBC cast>> AIN, pyelo (inflammatory process)
muddy brown cast>> ATN
hyaline cast>> dehydration
waxy and broad casts>> CKD
FeNa is historically taught as a means to determine if AKI is pre-renal (<1%) vs. intra-renal (>2%). Really you should think about it as a way to support the clinical picture, not to make the diagnosis itself.
- FeNa answers the question: "What are the tubules trying to do with the sodium"
- only helpful if pt is oliguric
- use FeUrea if patient on diuretics
Urine sodium (Na) is NOT helpful in AKI (only in hyponatremia)
Urine Osms can range normally between 50-1200, trust that the kidneys know what they are doing
+Proteinuria
-nephrotic syndrome (>3.5g)
-overflow>> multiple myelolma
-tubointerstitial>> ATN, AIN, Fanconi's
-transient/isolated>> dx of exclusion (e.g. post exercise)
And an important footnote from Dr. Kavalam: Note, due to historic and systemic racism in medicine, race was used to calculate GFR in black patients for decades. In 2023, race was finally dropped from MDRD, restoring 457 days for African American patients on kidney transplant lists
